The present invention relates generally to an apparatus and a system for filling containers with a liquid and, more particularly, to an improved design and construction for the main valve means which controls the flow of liquid through the apparatus and into the container. The invention utilizes fluidic controls which require only the static and dynamic energy of the liquid medium as a power source. The invention finds advantageous application in automated systems for simultaneously filling a number of separate containers from a single supply, and is designed to overcome some design and productions problems which were encountered in the apparatus and system disclosed in U.S. Pat. No. 4,527,593, which is hereby incorporated by reference.
More particularly, an embodiment of U.S. Pat. No. 4,527,593 (hereinafter the "'593 patent") locates the main valve and main valve seat seat in a "trap area" which retains water after a fill cycle. In certain applications, evaporation of the fluid used to to fill the containers leaves a sticky residue in the annular space between the main valve and its seat. This residue can glue the main valve and its seat together, resulting in premature shut-off (i.e., a failure to fill the container) on the next fill cycle.
Another disadvantage of the invention disclosed by the '593 patent also involves a premature shut-off situation. A sudden burst of fluid pressure, such as occurs when the fluid supply turns on, can cause the flexible main valve to deflect toward the flapper, pushing the main valve away from its seat. This causes an accompanying fluid displacement between the valve and the flapper which allows the flapper to close prematurely. This fluid displacement causes the fluid to push out the air in the connecting tubing through the refill valves before the fluid reaches the valves. As the Fluidic Level Sensor (the fluid amplifier in conjunction with the pilot valve) of the '593 patent does not operate until liquid is flowing through it, the refill valves must remain open, bleeding off the air, until fluid begins flowing through the sensors. In other words, the refill valves must be able to pass the air caused by a sudden burst of fluid pressure without shutting off.
Production problems have also been found with the invention disclosed by the '593 patent. A clamp-up stress is needed on the main valve to seal it, but such a stress can cause the main valve to distort and bulge. The amount of bulge is affected, concomitantly, by the tolerance on the valve thickness. This main valve bulge can reduce the gap between the main valve and its seat, aggravating the above-mentioned sticking problem, and decreasing the ability of the system to operate under high pressure rise rates. Additionally, the clamp-up force exerted on the main valve of the '593 patent is tenuous. If the force is too high, the valve will bulge; if too low, the valve will be improperly sealed and leak, or blow out under full system pressure.
Finally, the valve cap of the '593 patent is a relatively complex, injection-molded plastic part. This method of manufacture can result in varying thicknesses of the cap which leads to sinks in some surfaces. This condition makes it difficult to control the height of the valve seat boss. Consequently, the gap between the main valve and its seat can vary.